Method for treating actinic keratosis with cytotoxic agents

ABSTRACT

A method for treating actinic keratosis comprising applying an effective amount of a cytotoxic drug dispersed in a pharmaceutically acceptable vehicle containing a penetrating solvent for the drug, the drug being applied to the skin area having the actinic keratosis growth without occlusion in pulses at an interval of once every from 3 to 30 days and preferably at an interval of from 4 to 14 days. Optimally, the penetrating solvent is free from toxic effects, such as AZONE or similar substituted azacycloalkyl-2-ones, tertiary amine oxides, and the like.

FIELD OF THE INVENTION

This invention relates to the therapeutic treatment of skin disorders such as actinic keratoses. In particular, this invention relates to an effective regimen for successfully treating actinic keratoses with a cytotoxic agent such as fluorouracil (5-fluorouracil or 5--FU) in a penetrating solvent.

BACKGROUND OF THE INVENTION

Actinic keratosis is a horny growth, such as a wart or callosity on the skin, generally sharply outlined, red or skin-colored, flat or elevated, verrucous or keratotic growth, which may develop into a cutaneous horn, or may give rise to squamous cell carcinoma. It usually affects the middle-aged or elderly, especially those of fair complexion and is caused by excessive exposure to the sun.

Traditional treatments of actinic keratosis have included daily or more frequent application of cytotoxic agents such as fluorouracil with or without an occlusive dressing, dissolved or suspended in an ointment, lotion, or glycol solvent applied to the affected area. Penetrating solvents have been investigated for enhancing percutaneous absorption of fluorouracil in an effort to more successfully treat more resistive conditions.

Severe skin inflammation from damage to treated tissue by the cytotoxic agent typically occurs with this treatment, severely limiting its usefulness.

DESCRIPTION OF THE PRIOR ART

Fluorouracil (5-fluorouracil or 5--FU) is described as useful for the treatment of actinic keratosis, applied topically as a 1% cream or solution, once or twice daily, to the affected area in REMINGTON'S PHARMACEUTICAL SCIENCES. Mack Publishing: Easton, 15th ed. p 1079 (1975).

AZONE (1-dodecylazacycloheptan-2-one) is reported to enhance the percutaneous absorption of a variety of drugs including cortiocosteroids such as betamethazone and cytotoxic agents such as fluorouracil by Stoughton, R., Arch. Dermatol. 118: 474-477 (1982). Prior reports of dimethyl sulfoxide (DMSO), dimethylacetamide (DMA), dimethyl formamide (DMF), 1-methyl-2-pyrrolidone, and propylene glycol for enhancing percutaneous absorption of drugs was also indicated.

Comparison of AZONE with other penetrating solvents such as propylene glycol and n-decylmethyl sulfoxide for enhancing penetration of fluorouracil is described by Touitou, E., International Journal of Pharmaceutics. 27: 89-98 (1985). The writer characterizes 5--FU as a cytotoxic agent used topically on the skin in actinic kerotosis and various epithelial neoplasma, and states that the need for improved therapy brought into use methods for increasing skin penetration such as use of occlusivity and chemical enhancing agents, citing Chen, Y., NOVEL DRUG DELIVERY SYSTEMS. Marcel Dekker: New York, p 192 (1982). Propylene glycol solutions were said to be the most popular, and the writer's presentation demonstrated that AZONE was a more effective penetrating agent than propylene glycol or n-decylmethyl sulfoxide in dilute concentrations. Sogibayashi, K. et al, J. Pharm. Pharmacol. 37: 578-580 (1985) and Mourmoto, Y. et al, International Journal of Pharmacology. 32: 31-38 (1986) also describe enhanced absorption with AZONE across hairless rat skin, using 5-fluorouracil as a model drug.

U.S. Pat. No. 3,989,816 describes n-alkylazacycloheptan-2-ones wherein the alkyl group has from 1 to 18 carbons, and the use of these and related compounds to enhance percutaneous absorption or penetration of drugs. Among the extensive lists of drugs are antineoplastic agents such as fluorouracil. U.S. Pat. Nos. 3,989,815 and 3,991,203 describe use of bis-azacyclopentan-onyl alkanes and 1-substituted azacyclopentan-2-ones, respectively, as penetrating agent. In a disclosure almost identical to U.S. Pat. No. 3,989,816, the inventor lists fluorouracil as a suitable antineoplastic agent for use with the penetrating solvents.

U.S. Pat. No. 2,802,005 claims fluorouracil and describes it use as a germicidal agent or antimetabolite.

U.S. Pat. No. 4,565,806 describes treatment of skin cancer with cytostatic agents such as fluorouracil, colchicine, vinblastin sulfate, phloridzin, triethylene thiophosphamide, humic acid, and nitrogen mustards such as cyclophosphamide and mechlorethamine in DMSO. Percutaneous or intravenous administration are described. Suitable dosage levels and frequency recommended are said to be known to those skilled in the art.

U.S. Pat. No. 4,411,893 describes a novel water-soluble tertiary amine oxide useful to enhance of penetration of drugs through the skin. U.S. Pat. No. 3,326,768 is cited in the patent to show the use of a phosphine oxide surfactant in a topical preparation. U.S. Pat. No. 3,472,931 is also referenced, disclosing the use of a vehicle containing a lower alkyl amide to enhance percutaneous absorption. Use of the absorption enhancers with 5-fluorouracil for the treatment of actinic keratosis is also disclosed.

U.S. Pat. No. 3,996,924 describes the treatment of psoriasis with a combination of corticosteroid and 5-fluorouracil in a suitable topical ointment or solution carrier. Included in an omnibus listing of possible carrier ingredients are propylene glycols, dimethyl sulfoxide and dimethyl formamide. Daily application, preferably with a continuous occlusive dressing is recommended.

The prior art describes the application of cytotoxic agents in penetrating solvents applied once or more daily. Concurrent use with an occlusive dressing is indicated. In fact, the extreme inflammatory reaction caused by the cytotoxic damage to treated skin using daily dosing schedules with traditional vehicles has heretofore prevented the practical use of these new solvent systems to enhance percutaneous absorption of cytotoxic agents. When cytotoxic drugs such as fluorouracil are used to treat actinic keratosis, the traditional propylene glycol containing media are usually selected, applied once or more daily, and possibly with an occlusive dressing. Even with these milder systems, the inflammatory response severely limits the treatments.

SUMMARY OF THE INVENTION

This invention is a method for treating actinic keratosis comprising applying to an actinic keratosis growth, an effective amount of a cytotoxic drug dispersed in a pharmaceutically acceptable vehicle containing a penetrating solvent for the drug. The drug is applied in a pulse of from 1 to 3 applications within a period of 48 hours to the actinic keratosis growth without occlusion, and no further application is made for a period of from 3 to 30 days. This procedure is repeated until complete remission is effected.

Optimally, the penetrating solvent is free from toxic effects, such as AZONE or similar substituted azacycloalkyl-2-ones, tertiary amine oxides, and the like.

DETAILED DESCRIPTION OF THE INVENTION

In the method of this invention, a cytotoxic drug, in a vehicle containing a penetrating solvent, is applied topically to a skin area affected by actinic keratosis.

This invention is based on the discovery that with effective delivery of a cytotoxic agent through the stratum corneum, a superior therapeutic response is obtained if an effective amount drug is administered in one 48 hour pulse followed by a sustained pause of from 3 to 30 days and preferably from 4 to 14 days. During the 48 hour pulse period, the drug can be applied to the actinic keratosis growth a sufficient number of times to achieve the desired tissue concentration, usually from 1 to 3 times being sufficient. Most optimally, a single application of drug is made to the lesion once a week. Effective remission is obtained, usually within 30 days, without significant inflammation or other evidence of severe damage to treated tissue.

An effective method for achieving this result is the topical application of an effective concentration of the cytotoxic agent together with a penetrating solvent such as AZONE, water-soluble tertiary amie oxide, DMSO or the like as a "pulse application" at an interval of from 3 to 30 and preferably at an interval of from 4 to 14 days. During the 48 hour pulse period, the drug-penetrating solvent preparation is applied for a sufficient number of times to achieve the desired drug concentration in the tissue. With most actinic keratosis growths, the desired drug concentration can be achieved by from 1 to 3 applications of the drug-penetrating solvent composition.

In the method of this invention, a cytotoxic drug, in a vehicle containing a penetrating solvent, is applied topically to a skin area with the actinic keratosis growth.

Suitable cytotoxic agents include 5-fluorouracil, colchicine, vinblastine sulfate, cyclophosphamide, azathioprine, cyclocytidine, azocytidine, azaserine, cisplatin, cycloheximide, mechlorethamine, cycloleucine, cytarabine, decarbazine, dactinomycin, dichloromethotrexate, emetrine hydrochloride, etoposide, quanazole, hydroxyurea, idoxuridine, mercaptopurine, methotrexate, methyl GAG (methylglyoxal bis(guanylhydrazone)), metoprine, pyrimethamine, scopolamine hydrobromide, thioquanine, thiotepa, vincristine sulface, and cyclosporin A, 5-fluorouracil being preferred.

Suitable penetrating solvents are solvents for the cytotoxic agent which will enhance percutaneous penetration of the drug. Solvents which have this property include dimethyl sulfoxide, dimethylacetamide, dimethyl formamide and 1-methyl-2-pyrrolidone, and to a far lesser extent, propylene glycol. Preferred and superior solvents for this purpose are essentially free from adverse side effects and include substituted azacycloalkan-2-ones having from 5 to 7 carbons in the cycloalkyl group such as 1-dodecylazacycloheptan-2-one (AZONE) and other azacycloalkan-2-ones described in U.S. Pat. No. 3,989,816 (hereby incorporated by reference in it entirety) and represented by Formula I: ##STR1## wherein R¹ is a straight or branch chain alkyl group having from 1 to 18 carbons or aryl group having from 6 to 10 carbons;

R² is H or lower alkyl having from 1 to 4 carbons; and

n is an integer from 0 to 10.

Also included are N-bis-azacyclopentan-2-onyl alkanes described in U.S. Pat. No. 3,989,815 (hereby incorporated by reference in its entirety) and represented by Formula II: ##STR2## wherein R³ and R⁴ are each H or a lower alkyl group having from 1 to 4 carbons; and

m is a positive integer of from 1 to 18.

Also included are 1-substituted azacyclopentan-2-ones described in U.S. Pat. No. 3,991,203 (hereby incorporated by reference in its entirety) and represented by Formula III: ##STR3## wherein R⁵ and R⁶ are each H or lower alkyl having from 1 to 4 carbons; and

o is a positive integer from 0 to 10.

Also included are water-soluble tertiary amine oxides describe in U.S. Pat. No. 4,411,893 (hereby incorporated by reference in its entirety) and represented by Formulas IV and V: ##STR4## wherein R⁷, R⁸ and R⁹ are each saturated or unsaturated aliphatic radicals optionally containing ether or amide linkages and pendent hydroxyl groups, and the total number of carbon atoms of R⁷, R⁸ and R⁹ does not exceed 28. ##STR5## wherein X is --O-- or --N(R¹¹)--;

R¹⁰ and R¹¹ are each saturated or unsaturated aliphatic radicals having from 1 to 18 carbons and optionally containing ether or amide linkages and pendent hydroxyl groups; and

p is 0 or 1;

q is 2, 3 or 4; and

r is 2 or 3.

The topical formulation can be in the form of a lotion, cream, ointment, gel or solution, preferably a lotion, cream or solution containing a therapeutically effective amount of the cytotoxic drug and a sufficient proportion of penetrating solvent to solubilize the drug. Suitable drug concentrations will depend upon the choice of drug. Fluorouracil concentrations are from 0.001 to 5 weight percent and preferably from 1 to 5 weight percent.

For formulations with penetrating solvent of Formulas I, II and III, solutions or gels containing from 0.001 to 5 weight percent and preferably from 1 to 5 weight percent fluorouracil are preferred.

For formulations with penetrating agents such as the tertiary amine oxides of Formulas IV and V, the amine oxide and drug is incorporated into traditional lotions, gels and creams containing from 0.1 to 70 weight percent amine oxide, other traditional excipients, and water are preferred. These compositions can contain from 1 to 99 weight percent water.

A typical gel may contain, for example, one percent hydroxyethyl cellulose.

Typical lotion and cream formulations follows:

    ______________________________________                                         LOTION                                                                         Parts by Weight Ingredient                                                     ______________________________________                                         5               polyoxylene-40-stearate                                        3               sorbitan monostearate                                          12              *mixture of lanolin, mineral                                                   oil and lanolin alcohol                                        6               cetyl alcohol                                                  20              soybean oil                                                    53.7            water                                                          0.2             methyl paraben                                                 0.1             propyl paraben                                                 ______________________________________                                          *AMERCOL BL (Amerchol Corp, Edison, N.J.)                                

    ______________________________________                                         CREAM                                                                          Parts by Weight Ingredient                                                     ______________________________________                                         3               polyoxyethylene-4-stearate                                     2.5             sorbitan monostearate                                          10              soybean oil                                                    10              *mixture of lanolin, mineral                                                   oil and lanolin alcohol                                        1               cetyl alcohol                                                  73.2            water                                                          0.2             methyl paraben                                                 0.1             propyl paraben                                                 ______________________________________                                          *AMERCOL BL (Amerchol Corp, Edison, N.J.)                                

The composition containing the cytotoxic agent and penetrating solvent are applied to the skin area having the actinic keratosis growth in a quantity sufficient to wet or to cover the surface.

A critical aspect of this invention is the interval between pulses. In contrast to the previous methods of applying these agents, in penetrating solvents, they are applied according to this invention in single pulses at intervals of from 3 to 30 days and preferably at intervals of from 4 to 14 days. The procedure is repeated until the condition disappears. A total of from 1 to 4 application pulses is usually sufficient with fluorouracil.

When applied in accordance with this invention, the actinic keratosis growth disappears without extensive severe inflammation (erythma) of the treated skin surface. For patients with particular sensitivity to the cytotoxic agent, applications at longer intervals within the suggested range is suggested. If erythma begins to appear, the intervals should be lengthened until all signs of significant skin irritation disappear.

Occlusion is usually not necessary with the method of this invention. In a situation where the use of occlusion is believed necessary, the intervals between application times should be lengthened since cytotoxic agent damage to treated cells is usually increased by occlusive dressings.

Because the patient response will vary from patient to patient, the following examples include procedures for optimizing the parameters of drug concentration, number of applications per pulse, and the intervals between pulses. The preparations are applied initially once a week to the actinic keratosis growths in an amount sufficient to moisten the surface. Depending upon the patient's response to the therapy, the physician can elect to continue the therapy in the same manner if progress is satisfactory or elect to vary any of the parameters. The concentration of drug and penetrating agent can be varied until the desired amount of drug concentration in the tissue is obtained. Initially, one application per pulse can be used, and the period of exposure of the lesions to the drug is selected to achieve the desired amount of drug concentration in the tissue. The number of applications per pulse and the duration of the interval between pulses is determined by the response of the actinic keratosis to treatment and the time required for the treated skin to recover from exposure to the drug, timed to minimize local toxicity.

Once remission is achieved, physicians may choose two courses of treatment during remission. Preferably, no therapy is applied until relapse occurs. Then an appropriate therapy schedule is reinstated. Alternatively, in order to maintain a remission, maintenance therapy may be selected, applying drug/penetrating agent compositions delivering the lowest effective dose of drug with the longest intervals between applications still providing effective remission.

This invention is further illustrated by the following specific but non-limiting examples. In the examples, temperatures are given in degrees Centigrade and concentrations are given as weight percents, unless otherwise indicated. Examples constructively reduced to practice in filing this application are presented in the present tense, and examples describing procedures carried out in the laboratory or clinic are set forth in the past tense.

EXAMPLE 1 Titration of Drug Treatment Parameters

Solution A is prepared comprising 1 wt.% 5--FU, 2 wt.% AZONE, 50 wt% propylene glycol and the remainder, sterile, deionized water.

Solution A is applied an actinic keratosis growth once weekly in an amount sufficient to moisten the surface. If, at the end of two weeks, the response to the treatment is less than desired, a more concentrated solution (Solution B) is prepared containing 5 wt.% 5--FU, 2 wt.% AZONE, 50 wt.% propylene glycol and the remainder sterile, deionized water.

If the progress is still unsatisfactory, the application regiment is modified. Two applications of Solution B are applied in a pulse of two applications 12 hours apart. The interval between pulses is left unchanged. If the rate of progress is satisfactory, and no local toxicity is observed, the regimen is repeated with this concentration until complete remission is achieved.

EXAMPLE 2 Optimizing Pulse Timing Cream Composition

Cream A is prepared containing 5 wt.% 5--FU, 40 wt.% 1-benzylazacyclopentan-2-one and the remainder inert excipients which provide a stable cream composition (AMERCOL BL, described above).

Cream A is applied once weekly to an actinic keratosis growth in an amount sufficient to moisten the surface. If after 2 weeks the rate of progress is satisfactory but there is evidence of mild, local toxicity, a rest period of no therapy is instituted for one week to allow recovery from the toxicity. Treatment is then reinstated changing the interval between pulses to 2 weeks, leaving the formula and number of applications unchanged. If after 2 weeks, the rate of recovery is satisfactory, and no local toxicity is observed, the program is continued until remission is achieved.

EXAMPLE 3 Optimizing Lotion Composition

Lotion A is prepared with the following composition: 5--FU, 1 wt.%; N-bis-1,6(azacyclopentan-2-onyl)hexane, 20 wt%.; cetyl alcohol, 15 wt.%; propylene glycol, 10 wt.%; sodium lauryl sulfate, 15 wt.%; and sterile, deionized water qs. ad.

The patient begins treatment with the lotion applied once a week in an amount sufficient to moisten the surface of the actinic keratosis growth. If after 2 weeks, the rate response is inadequate though no local toxicity is observed, Lotion B is prepared having the following ingredients: 5--FU, 5 wt.%; N-bis-1,6(azacyclopentan-2-onyl)hexane, 20 wt%.; cetyl alcohol, 15 wt.%; propylene glycol, 10 wt.%; sodium lauryl sulfate, 15 wt.%; and sterile, deionized water qs. ad. Lotion B is applied once a week in an amount sufficient to moisten the surface.

If after 2 weeks, the rate of response is still inadequate without local toxicity, the number of applications per pulse is increased to 3 separate applications with a separation of 12 hrs between applications, with no change in formula or interval between pulse doses. If after 2 weeks, the rate of progress is improved, but slight local toxicity is observed, the interval between pulses is increased to 2 weeks with the other parameters remaining unchanged.

If after two weeks, the rate of progress is adequate and no local toxicity is observed, the therapy regimen in repeated without change until complete remission occurs. 

I claim:
 1. A method for treating actinic keratosis consisting essentially of applying a therapeutically sufficient quantity of a composition consisting essentially of 5-fluorouracil dissolved in a penetration enhancing agent to an actinic keratosis growth until remission occurs, the composition being applied in one or more pulses at about one week intervals, each pulse comprising applying to the growth one or more times over a period of up to 48 hours, an amount of the composition sufficient to wet the lesion.
 2. The method of claim 1 wherein the penetration enhancing agent includes propylene glycol.
 3. The method of claim 2 wherein a solution of from 0.001 to 5 wt.% 5-fluorouracil in propylene glycol is applied to the actinic ketatosis growth.
 4. The method of claim 1 wherein the penetration enhancing agent includes a compound of Formula I, II or III: ##STR6## wherein R¹ is a straight or branch chain alkyl group having from 1 to 18 carbons or aryl group having from 6 to 10 carbons;R² is hydrogen or lower alkyl having from 1 to 4 carbons; and n is an integer from 0 to 10; ##STR7## wherein R³ and R⁴ are each hydrogen or a lower alkyl group having from 3 to 4 carbons; and m is an integer from 1 to 18; or ##STR8## wherein R⁵ and R⁶ are each hydrogen or lower alkyl having from 1 to 4 carbons; and o is an integer from 0 to
 10. 5. The method of claim 4 wherein the penetration enhancing agent is a compound of Formula I.
 6. The method of claim 5 wherein the penetration enhancing agent is 1-dodecylazacycloheptan-2-one. 